The cable stretching tool when building up a bike? I am building my first bike. I have owned, ridden, loved, done minor repairs on my bikes, I can tune up my own, even helped my buddy put together a bike.
I REALLY want to do this, so can anyone tell me if this tool is nescessary, a friend said no what do you think. I figure I have most of the tools I will need already. Hex wrenches, chain tool, work stand, lockring tool. I figure all I will really need to by is a BB tool for Mega-Exo crank. Dont think I will need cable cutters as I can use a dremel tool. Also I have used a reguler Park CT-3 chain tool on 9spd Campy chains, will this tool also work on the 10spd as well, I really dont feel like giving $100 for a chain tool.
In the end all I really want the shop to do is cut and install the fork, headset bearings and such. I just dont feel comfy cutting the carbon tube.

Just build the bike and when its done go for a ride or two on it... By then, the cables would have stretched and retune the deraillieurs...

I assume that you're talking about a "fourth hand" tool. I used to occassionally use one for old style canty brakes but I can see no use for one on a modern road bike. A decent cable cutter, however, is priceless.

I have used a dremel tool a lot building RC cars and those cutting wheels really aren't all that great for cutting something like cables. A good pair of cable cutters aren't expensive and leave the cable ends very smooth so they go through the housing with no snags.
Having a proper BB tool is good to, but if you have to take the frame to your LBS anyway to get the headset and fork work done, you may as well let them face the BB shell, clean up the threads if needed, and install the Bottom Bracket for you. Then you can install the crankset at home.

The 10 speed chain does not install the same as a 9 speed. You don't need a special chain tool, but there is a special connecting pin that can only be pushed in ONCE. Read the instructions and remove links from the correct end of the chain. The trick to installing the pin without the special tool is to drape the chain over the bottom bracket shell to eliminate any tension on the chain while installing the pin from the left side, per the instructions. The better option is to just buy a wipperman connex link for no-tool joining of the chain.

The cable stretching tool is definitely not needed. The easy way to get sufficient tension on a brake cable is to screw the cable adjuster out about 2 turns from the mid point, then grasp the pads and squeeze them tight against the rim. Pull on the cable with your fingers, the tighten the clamp bolt. When you release your grasp of the pads, they should be too close to the rim. Then all you have to do is screw the cable adjuster in a couple of turns to loosen the cable and bring the pads into proper adjustment.

If you've got a threadless integrated headset, it may require no tools to install.

As others noted, get some cable cutters. When you slip with that dremel tool and gouge the frame, brakes or derailleurs with it, you'll wish you had.

Cutting a fork is a very easy job with a fine blade hacksaw. The mistake that most people make is trying to measure the correct length. No measuring is required. Just assemble the fork, headset and stem with the amount of spacer that you want under the stem, pressing down hard on the stem to seat everything. Then scribe a line around the top of the stem. Remove the fork and cut about 2mm above the line. Make a shallow cut AROUND the outside of the tube, about 90 degrees at a time, following the line. After you've gone all the way around, cut deeper, until you're all the way through, working your way around as before. The cut should be straighter than trying to cut from top to bottom. When done, lightly file or sand the edges to remove burrs. When the fork is reinstalled, put an additional 5mm spacer on top to insure a gap between the top cap and steering tube.

Here's the right way to adjust chain length. A simple job that many find to be mysterious.

Two simple tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination; remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on itself or the chain guide tab as it passes under the upper derailleur pulley. If you want to see how much lower pulley movement will occur, without removing the extra inch of chain, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity.

Second, the chain must be long enough to avoid over-extending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated wrap capacity. If you deliberately exceed the derailleur's capacity and the derailleur is over-extended in the big ring/largest cog combo, then you must either avoid that combo or add another inch and avoid using the little chainring and the smallest 3 or 4 cogs (since the chain will hang loose).

No disagreement with anything said except that I have found that the fourth hand or third hand or whatever it's called is handy. it's not necessary, but it's handy. You can clamp it on the cable as you would vice grips to hold the cable in place while you tighten the bolt. If you're righthanded, you end up having to cross hands or use your left hand to tighten derailer cables otherwise. Not a big deal, but I think it's worth the twenty bucks or whatever it is.

. . . but the tool that Park makes for holding the brake pads down or whatever it does while you tighten down the brake cables I found to be useless. That one I regret buying. Tried to use it once or twice a few years ago. I forget even what it's supposed to do.

The 10 speed chain does not install the same as a 9 speed. You don't need a special chain tool, but there is a special connecting pin that can only be pushed in ONCE. Read the instructions and remove links from the correct end of the chain. The trick to installing the pin without the special tool is to drape the chain over the bottom bracket shell to eliminate any tension on the chain while installing the pin from the left side, per the instructions. The better option is to just buy a wipperman connex link for no-tool joining of the chain.

The cable stretching tool is definitely not needed. The easy way to get sufficient tension on a brake cable is to screw the cable adjuster out about 2 turns from the mid point, then grasp the pads and squeeze them tight against the rim. Pull on the cable with your fingers, the tighten the clamp bolt. When you release your grasp of the pads, they should be too close to the rim. Then all you have to do is screw the cable adjuster in a couple of turns to loosen the cable and bring the pads into proper adjustment.

If you've got a threadless integrated headset, it may require no tools to install.

As others noted, get some cable cutters. When you slip with that dremel tool and gouge the frame, brakes or derailleurs with it, you'll wish you had.

Cutting a fork is a very easy job with a fine blade hacksaw. The mistake that most people make is trying to measure the correct length. No measuring is required. Just assemble the fork, headset and stem with the amount of spacer that you want under the stem, pressing down hard on the stem to seat everything. Then scribe a line around the top of the stem. Remove the fork and cut about 2mm above the line. Make a shallow cut AROUND the outside of the tube, about 90 degrees at a time, following the line. After you've gone all the way around, cut deeper, until you're all the way through, working your way around as before. The cut should be straighter than trying to cut from top to bottom. When done, lightly file or sand the edges to remove burrs. When the fork is reinstalled, put an additional 5mm spacer on top to insure a gap between the top cap and steering tube.

Here's the right way to adjust chain length. A simple job that many find to be mysterious.

Two simple tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination; remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on itself or the chain guide tab as it passes under the upper derailleur pulley. If you want to see how much lower pulley movement will occur, without removing the extra inch of chain, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity.

Second, the chain must be long enough to avoid over-extending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated wrap capacity. If you deliberately exceed the derailleur's capacity and the derailleur is over-extended in the big ring/largest cog combo, then you must either avoid that combo or add another inch and avoid using the little chainring and the smallest 3 or 4 cogs (since the chain will hang loose).
I will go ahead and get the cable cutters. I cant wait to start on it.

You really won't regret the cable cutters. Heck just getting that oh-so-perfect divot in your cable ends is worth a trophy beer in itself. :D

I will go ahead and get the cable cutters. I cant wait to start on it.
Make sure you get the right cutters. Modern cable housing cutters are made to cut derailleur housing easily in addition to spiral brake housing and of course cables. There are some plain old cable cutters (much less expensive) which are made to only cut cables and perhaps spiral brake housing. I have the Park cable housing cutter but I often use my Dremel to cut the housing (super clean and no filing needed) and then my old Park cable cutters to cut the cables. So if you have a Dremel you could get away with the cheap cable cutters to go with it. Just something to think about.

Dave